the dried, unopened flower buds of eugenia caryophyllus (sprengel) bullock et. Harrison (formerly eugenia caryophyllata thunberg). The dried buds resemble a round-headed nail, are dark reddish-brown in color, have a strong aromatic odor, and a hot pungent, aromatic taste. The principal active ingredient in the volatile oil is eugenol. The quality characteristics are measured by volatile oil, total and acid insoluble ash, moisture, and freedom from clove stems.